We propose to examine the relationship between air pollution and pregnancy outcome in New York City (NYC) to help determine whether there is a causal link, focusing on the effect of particulate air pollution on preterm birth and reduced fetal growth. There is increasing evidence that levels of particulate air pollution currently experienced in urban areas of the U.S. may have adverse effects on the course and outcome of pregnancy, which would be of great clinical and public health significance. The proposed study will integrate data collected for the New York City Community Air Survey (NYCCAS) with birth records linked to hospital discharge data for approximately 300,000 NYC residents who delivered in calendar years 2007-2009. Based on a rigorously designed survey of 150 locations in NYC, the NYCCAS has developed comprehensive, validated models to estimate levels of ambient fine particulate matter (PM2.5) air pollution and its source constituents, as well as other potentially correlated pollutants throughout the city. Birth records obtained from the NYC Department of Health and Mental Hygiene, including geocoded residence for assigning exposure, will be linked to hospital discharge data for refined classification of the pregnancy outcomes of interest, preterm birth, fetal growth, and pregnancy-induced hypertension, a key determinant. Indicators of socioeconomic status (SES) and other potential confounders are available at the individual level from birth certificates (education, smoking status) and hospital discharge data (insurance coverage), and on an aggregate level for the Census Tract of residence (indices of SES). With this information, we will assess whether PM2.5 and its constituents are related to risk of preterm birth, reduced birthweight, and pregnancy-induced hypertension. With these data resources, we will be able to overcome major limitations of past studies by evaluating the role of particulate constituents and sources, examining subsets of preterm birth based on severity and clinical presentation, and identifying critical time windows during pregnancy when adverse effects are observed. Through these efforts, we will be able to substantially advance our understanding of the hypothesized causal link between air pollution and pregnancy outcome, addressing a question of substantial public health and regulatory importance.